Abstract: Disclosed herein are aspects of methods to control airflow to a fuel cell stack and a cooling fan within a housing by fluidly connecting a predetermined minimum volume of airflow through the housing to the fan and a series of louvres, adjustable apertures, and bypass valves dynamically adjust the air flow to at least one of one of the fuel cell stack and fan providing the required minimum volume of fluid to the fan during different controller based modes of operation.

Abstract: An automated tutoring platform, system and method configured to permit students to find and contact, in real time, other students or persons with subject matter expertise in a particular area and to directly connect with such persons to purchase and obtain tutoring services online through the automated tutoring system and method. The automated tutoring system and method is configured to provide an on-line or virtual marketplace or exchange where students can interact, discuss topics of interest, send and receive messages, find qualified and pre-vetted subject matter experts, students or other persons with relevant experience for a tutoring session or sessions and to receive such tutoring sessions virtually through the automated tutoring platform, system and method.

Abstract: A box frame hub arm structure is provided and includes a body having an outboard surface, which is disposable to abut with an inboard surface of an outboard arm of an aircraft rotor head, and lead/lag sides. The body is formed to define a first cavity, an aperture communicative with the first cavity through the outboard surface and second and third cavities. The second and third cavities extend outwardly in opposite lead/lag directions from the first cavity to the lead/lag sides.

Abstract: A blade retention system includes a rotor hub including a plurality of radial arms, and a blade retention yoke associated with the rotor hub and one of the plurality of radial arms. The blade retention yoke is rotatable relative to the rotor hub and the radial arm. A tension torsion device connects the radial arm to the blade retention yoke to restrict radial movement of the blade retention yoke relative to the radial arm.

Abstract: A box frame hub arm structure is provided and includes a body having an outboard surface, which is disposable to abut with an inboard surface of an outboard arm of an aircraft rotor head, and lead/lag sides. The body is formed to define a first cavity, an aperture communicative with the first cavity through the outboard surface and second and third cavities. The second and third cavities extend outwardly in opposite lead/lag directions from the first cavity to the lead/lag sides.

Abstract: A retaining assembly for a tail rotor system is provided including a washer having a plurality of splines. The washer is configured to couple to an adjacent pitch change shaft. A retaining nut includes a self-locking feature and a flange arranged at a first end. The retaining nut is configured to threadably couple to the pitch change shaft such that the flange is in contact with the washer. The flange includes a plurality of first holes configured to at least partially align between the splines of the washer. A lock plate includes a body and a plurality of tabs extending generally perpendicularly from the body. The lock plate is slidably positioned about the pitch change shaft adjacent the flange. The lock plate is operably coupled to the retaining nut and the washer to limit rotational movement thereof relative to the pitch change shaft.

Abstract: A retaining assembly for a tail rotor system is provided including a washer having a plurality of splines. The washer is configured to couple to an adjacent pitch change shaft. A retaining nut includes a self-locking feature and a flange arranged at a first end. The retaining nut is configured to threadably couple to the pitch change shaft such that the flange is in contact with the washer. The flange includes a plurality of first holes configured to at least partially align between the splines of the washer. A lock plate includes a body and a plurality of tabs extending generally perpendicularly from the body. The lock plate is slidably positioned about the pitch change shaft adjacent the flange. The lock plate is operably coupled to the retaining nut and the washer to limit rotational movement thereof relative to the pitch change shaft.

Abstract: The invention provides optical elements having a substrate with a textured surface, and a coating disposed on the textured surface. The coating is a multi-layer optical coating that provides desirable optical properties for the optical element. The coating is conformally disposed on the textured surface of the substrate. The invention also provides methods for making and methods for using such optical elements.

Abstract: A method of making a polypropylene base fabric for outdoor use, and the fabric so produced, results in an outdoor use product (such as a furniture cover) having high mechanical durability, improved hand, excellent color durability, and lower soiling than comparable conventional products. The method is practiced using yarn comprising or consisting of polypropylene, UV inhibitor, and fluorochemical by: weaving the yarn using heavier yarn in the warp direction and finer yarn in the filling direction, or yarns of substantially equal size or denier in the warp and filling directions, to produce a fabric with a face, a center, and a back, with at least 50% (e.g. about 50-70%) of the filling yarn exposed to the fabric face (and for example about 6-10% in the center and about 20-40% in the back); washing the fabric with detergent and water to scour off the spin finish on the yarns; and drying the washed fabric at a temperature below the softening point of polypropylene (e.g. about 270-280° F.